I. Field
The present disclosure relates generally to communication, and more specifically to techniques for mitigating interference in a wireless communication system.
II. Background
A wireless multiple-access communication system can concurrently support communication for multiple terminals on the downlink and uplink. The downlink (or forward link) refers to the communication link from the base stations to the terminals, and the uplink (or reverse link) refers to the communication link from the terminals to the base stations. Multiple terminals may simultaneously transmit data on the uplink and/or receive data on the downlink. This may be achieved by multiplexing the data transmissions on each link to be orthogonal to one another in time, frequency, and/or code domain. The orthogonality ensures that the data transmission for each terminal minimally interferes with the data transmissions for other terminals.
A multiple-access system typically has many cells, where the term “cell” can refer to a base station and/or its coverage area depending on the context in which the term is used. Data transmissions for terminals in the same cell may be sent using orthogonal multiplexing to avoid “intra-cell” interference. However, data transmissions for terminals in different cells may not be orthogonalized, in which case each terminal would observe “inter-cell” interference from other cells. The inter-cell interference may significantly degrade performance for terminals observing high levels of interference.
To combat inter-cell interference, a system may employ a frequency reuse scheme in which each cell uses only a portion of a frequency band available for the system. For example, the system may employ a 7-cell reuse pattern and a frequency use factor of 1/7. In this system, the frequency band is divided into seven frequency subbands, and each cell in a 7-cell cluster is assigned one of the seven frequency subbands. Each cell uses only one frequency subband, and every seventh cell reuses the same frequency subband. With this frequency reuse scheme, the same frequency subband is only reused in cells that are not adjacent to each other, and the inter-cell interference observed in each cell is reduced relative to the case in which all cells use the entire frequency band. However, a small frequency use factor (e.g., 1/7) represents inefficient use of the available system resources since each cell is able to use only a fraction of the frequency band.
There is therefore a need in the art for techniques to reduce inter-cell interference in a more efficient manner.